This invention relates generally to tankers for carriage of liquids such as oil and, more particularly, to apparatus for control of cargo leakage from a damaged tanker.
Internationally standardized regulations require that oil tankers greater than 20,000 tons deadweight be subdivided by longitudinal and transverse bulkheads arranged to form a plurality of tanks, some dedicated for carriage of cargo oil and some for sea water ballast. This arrangement is known as "segregated ballast" and replaces the previous practice of using tanks interchangeably for cargo oil and ballast, which frequently resulted in residual cargo oil being discharged overboard with ballast water.
In the event a fully loaded tanker of the "segregated ballast" type sustains damage by grounding or collision severe enough to rupture one or more of its cargo tanks, oil will flow out of the hull until the pressure of oil at the penetration is equal to the water pressure. Depending on the density of the oil relative to the density of the water, outflow usually stops when the oil level in the tank drops to just above the water level. As oil flows out from the damaged tank or tanks, the weight of the ship is reduced causing it to rise higher out of the water, and also heel and trim, thereby to reduce the draft at the area of damage, which further increases outflow of oil.
It is a primary object of the present invention to minimize the oil outflow from a damaged tanker of the "segregated ballast" type.